Many devices use joint arrangements to move one part of a device relative to another part of the device, such as moving between a collapsed configuration and an expanded configuration, rotating from one position to another, or performing more complicated manipulations. Joint arrangements can be designed to repeatedly move among configurations or positions, either for an infinite number of cycles or a finite number of cycles, or can be designed to move between configurations or positions only once or a limited number of times.
One approach for joint arrangements is to construct joints utilizing multiple parts where one part rotates relative to the other by means of sliding contact between components of the joint, such as a ball and socket or a pin and clevis. There are many known problems with such joints. Structures utilizing a plurality of multi-part joints can also suffer from a problem known as “dead band,” in which movement at one end of the structure is not communicated to the other end until the intervening clearances in the multi-part joints are taken up. Such joints can also be difficult and expensive to manufacture to the required tolerances.
In view of these problems with rigid multi-part joints, joint arrangements comprised of straps, bands or leaf springs of flexible materials have been used, such as described in U.S. Pat. Nos. 3,386,128, 4,869,552, 5,133,108, 5,196,857 and 6,378,172. U.S. Pat. Nos. 6,175,989 and 6,772,479 describe flexible joint arrangements that utilize shape memory alloy materials. A resilient joint is disclosed in U.S. Pat. No. 7,435,032 that limits the maximum strain on the joint by connecting the ends of a flexure to cavities that limit the bend radius of the flexure to ensure that the maximum strain is not exceeded. The flexure member connects two separate structures and functions essentially like a standard leaf spring that stores the energy used to move it to the collapsed configuration in order to return to the expanded configuration.
One of the significant drawbacks of conventional designs for flexible joint arrangements is that such joints generally cannot support any significant loading in either compression or tension, and are therefore unsuitable for devices that must support such loads.